54 lines
2 KiB
C++
54 lines
2 KiB
C++
/*
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* Copyright (c) 2019 BitShares Blockchain Foundation, and contributors.
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*
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* The MIT License
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include <fc/popcount.hpp>
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namespace fc {
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#if _MSC_VER || __GNUC__ || __clang__
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#else
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uint8_t popcount( uint64_t v )
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{
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// Public Domain code taken from http://graphics.stanford.edu/~seander/bithacks.html
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uint8_t c;
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static const int S[] = {1, 2, 4, 8, 16, 32};
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static const uint64_t B[] = {0x5555555555555555, 0x3333333333333333, 0x0F0F0F0F0F0F0F0F,
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0x00FF00FF00FF00FF, 0x0000FFFF0000FFFF, 0x00000000FFFFFFFF };
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c = v - ((v >> 1) & B[0]);
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c = ((c >> S[1]) & B[1]) + (c & B[1]);
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c = ((c >> S[2]) + c) & B[2];
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c = ((c >> S[3]) + c) & B[3];
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c = ((c >> S[4]) + c) & B[4];
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return ((c >> S[5]) + c) & B[5];
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}
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#endif
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uint8_t popcount( const uint128_t& v )
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{
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return popcount( static_cast<uint64_t>(v >> 64) )
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+ popcount( static_cast<uint64_t>(v & 0xffffffffffffffffULL) );
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}
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} // namespace fc
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